Working creatively to meet strict preservation codes, architect Roberto de Leon affixes a modern annex onto a historic Louisville house.

The living room in the original house has Victorian details, but the furniture—vintage Bertoia chairs, a Gloss floor lamp by Pablo Pardo, and a Norm 03 Steel Pendant Lamp by Normann Copenhagen—brings the look up to date.

The family room has wall-to-wall cabinets built by Bradford T. Newhall Construction, a local company that also served as the general contractor on the project. The stainless steel drawer pulls are by Sugatsune. The minimalist white-and-wood interior complements the couple's collection of mod furniture, which includes a vintage sofa by Edward Wormley for Dunbar and two cork tables by Jasper Morrison for Moooi.

Out of respect for the structure's more traditional neighbors, de Leon painted the exterior of the addition Black Forest Green, a Benjamin Moore hue commonly used on plantation shutters in the South.

Seeking a quieter and more kid-friendly existence, in 2007 Juliet Gray and Mathias Kolehmainen traded the glamour of the Hollywood Hills for Gray’s home­town of Louisville, Kentucky. Disappointed with the city’s meager stock of mid-century modern houses, they settled in a 2,200-square-foot “eclectic Victor­ian” in the Cherokee Triangle, an enclave of restaurants, shops, and historic homes on Louisville’s east side. Expanding their new living space with an addition was part of their plan from the start.

“We wanted a family room that was connected to, but not on top of, the kitchen,” Gray says, ticking off their wish list. “We also wanted outdoor space off the kitchen where we could eat, wide steps that would spill into the yard, and that indoor-outdoor relationship that can get lost in old homes with big walls and small windows. We wanted to open it up.”

The couple interviewed five architects before settling enthusiastically on Roberto de Leon of Louisville’s De Leon & Primmer Architecture Work­shop, drawn to his “clear understanding of how to use light and space in a thoughtful way,” says Gray.

From the outset, there were challenges. For one, the century-old house sits in a historic preservation district. De Leon and project manager David Mayo had to design a structure whose modern flair wouldn’t clash with its surroundings, while also passing muster with Louisville’s strict Historic Landmarks and Preservation Districts Commission.

De Leon and Mayo documented every structure within a six-block area, taking design cues from the lean-tos and semi-detached sheds found in many of the neighborhood’s backyards. They proposed cladding the addition in fiber-cement lap siding and painting it dark forest green, a color commonly found on historic Kentucky plantation houses. “That was a way for us to make a case for the scale of the addition, the materials, and even the detailing to the landmarks board as a way to say, ‘This is really in character with everything that’s around this neighborhood,’” de Leon says.

There were two large trees in the backyard—a hackberry and a pin oak—that Gray insisted on preserving. “That really impacted the footprint of the addition,” de Leon says. “It zigs and zags around those trees and, in the process, creates these little pockets for the kids to play in while allowing light to enter the existing house.”

Construction began in the spring of 2008—as Gray was about to have the couple’s second son—and was completed in January 2009 for around $200,000. Gray, an avid cook desiring a new kitchen to bridge the old house and the new space, was forced to rough it in the interim. “We had a portable range and a big toaster oven,” she says. “It was an adventure.”

De Leon took pains to carefully integrate the addition and the existing house. He aligned the back door with the front entrance, allowing light to penetrate deeper into the building’s core while increasing a sense of flow through the house. Between the dining room and a renovated bathroom in the original structure, de Leon carved out a new vestibule to serve as a transition point—a place where the residents can “decamp,” as de Leon puts it, when they enter the house, dropping off jackets and keys before emerging in the new kitchen and family room.

Outside, the dark shade of the addition complements the sage-green exterior of the existing house. Large windows let in ample natural light during the day and bathe the yard in artificial light at night. When the family has friends over, Gray and Kolehmainen project movies from a deck off the second floor onto the side of a detached carriage house, and everyone sits on the wide steps to watch. Today, they spend virtually all of their time in the new addition—that is, when they’re not outside admiring it from the backyard.

Juliet Gray, Mathias Kolehmainen, and their sons Cooper and Cyrus have a new favorite hangout: the wide back steps on the addition, which double as theater seating. (They project movies from the second-floor balcony onto an out-building across the yard.)

The cherry veneer cabinets carry into the streamlined kitchen where a Shepard Fairey print and a range by Wolf take pride of place. "We tried to make sure that all the wood used in the project looked seamless and uniform," says de Leon. "Wood was the only 'color' we introduced."